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USB: serial: ch341: fix modem-status handling

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The modem-status register was read as part of device configuration at
port_probe and then again at open (and reset-resume). During open (and
reset-resume) the MSR was read before submitting the interrupt URB,
something which could lead to an MSR-change going unnoticed when it
races with open (reset-resume).

Fix this by dropping the redundant reconfiguration of the port at every
open, and only read the MSR after the interrupt URB has been submitted.

Fixes: 664d5df92e ("USB: usb-serial ch341: support for DTR/RTS/CTS")
Signed-off-by: Johan Hovold <johan@kernel.org>
This commit is contained in:
Johan Hovold 2017-01-06 19:15:17 +01:00
parent 56e6d90797
commit a0467a967f
1 changed files with 12 additions and 15 deletions
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27
drivers/usb/serial/ch341.c
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@ -248,21 +248,11 @@ static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
if (r < 0)
goto out;
/* expect 0xff 0xee */
r = ch341_get_status(dev, priv);
if (r < 0)
goto out;
r = ch341_set_baudrate_lcr(dev, priv, priv->lcr);
if (r < 0)
goto out;
r = ch341_set_handshake(dev, priv->line_control);
if (r < 0)
goto out;
/* expect 0x9f 0xee */
r = ch341_get_status(dev, priv);
out: kfree(buffer);
return r;
@ -334,14 +324,9 @@ static void ch341_close(struct usb_serial_port *port)
/* open this device, set default parameters */
static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port)
{
struct usb_serial *serial = port->serial;
struct ch341_private *priv = usb_get_serial_port_data(port);
int r;
r = ch341_configure(serial->dev, priv);
if (r)
return r;
if (tty)
ch341_set_termios(tty, port, NULL);
@ -353,6 +338,12 @@ static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port)
return r;
}
r = ch341_get_status(port->serial->dev, priv);
if (r < 0) {
dev_err(&port->dev, "failed to read modem status: %d\n", r);
goto err_kill_interrupt_urb;
}
r = usb_serial_generic_open(tty, port);
if (r)
goto err_kill_interrupt_urb;
@ -619,6 +610,12 @@ static int ch341_reset_resume(struct usb_serial *serial)
ret);
return ret;
}
ret = ch341_get_status(port->serial->dev, priv);
if (ret < 0) {
dev_err(&port->dev, "failed to read modem status: %d\n",
ret);
}
}
return usb_serial_generic_resume(serial);